1. Field of the Invention
This invention relates to internal combustion engines, and more particularly concerns a kit having parts which allows the operation of an engine with its two balance shafts removed.
2. Description of the Prior Art
Numerous inline four cylinder engines have been disclosed in the prior art. A well known inherent shortcoming of this engine cylinder configuration has been the vibration caused by the unbalanced nature of cylinder firing. Various mechanisms have been employed in attempts to eliminate the jerky vibration of inline four cylinder engines. The most effective designs employ one or more counter-weighted balance shafts which are disposed within the engine block parallel to the crankshaft. Balance shafts are generally adapted to rotate at twice crankshaft speed, and harmonically cancel the inertial forces of the crankshaft and cylinders. For example, U.S. Pat. No. 4,594,757 discloses an engine which utilizes balance shafts.
Another engine having balance shafts is the Chrysler/Mitsubishi 2.6 liter engine. Upper and lower balance shafts which rotate at twice the speed of the crankshaft are timed to coincide with the firing of the cylinders, and harmonically cancel vibration. The upper shaft is driven directly from a balance shaft drive chain which is driven by a sprocket at the front of the crankshaft. The lower balance shaft is driven by the oil pump which is driven by said balance shaft drive chain. Although the balance shafts essentially perform their intended purpose, long term maintenance experience with this popular engine has revealed significant shortcomings. Most specifically, the engine's lubrication system does a poor job of oiling the bearings which support these balance shafts. Oil enters the upper balance shaft through an oil galley associated with one bearing bore only, which is located at the front of the engine. Oil enters the lower balance shaft through a passage in the oil pump drive gear. Oil travels though each shaft in order to reach the rear bearings supporting each shaft. Being that the balance shafts turn at twice the speed of the engine's crankshaft, the balance shafts require greater volumes of oil, which are just never delivered by an inadequate lubrication system.
The balance shaft drive chain is subject to wear, which may ultimately result in failure of the balance shaft drive altogether, including the oil pump. This of course is catastrophic to the engine. In many instances the lack of oil results in premature failure of the balance shaft bearings. Once the bearings in the balance shaft bores have seized to the shafts and spun in the bearing bores, the engine block is rendered unusable and may not be rebuilt. If the balance shaft bearings are not spun, a rebuilding of the engine requires replacement of balance shafts, bearings, sprockets, drive chain, tensioners and chain guides at considerable cost.
Many manufacturers and drivers of four cylinder vehicles have come to accept the vibration of an unbalanced engine as normal. Since the potential for catastrophic engine failure may far outweigh the benefits of reduced vibration, it is desirable to have a means for pre-emptively modifying the Chrysler/Mitsubishi 2.6 liter engine by eliminating the balance shafts and permitting otherwise normal operation of the engine. It is also desirable to have means for re-building a Chrysler/Mitsubishi 2.6 liter engine once the bearing journals have been irreparably damaged.
It is accordingly an object of the present invention to provide a retrofit kit for a Chrysler/Mitsubishi 2.6 liter engine which will permit the operation of the engine with its balance shafts removed.
It is another object of the present invention to provide a retrofit kit of the aforesaid type which will prevent the occurrence of catastrophic engine failure due to malfunction of the engines lubrication system.
It is yet another object of the present invention to provide a retrofit kit of the aforesaid nature to permit the usage of an engine block which has been rendered otherwise useless due to premature balance shaft bearing seizure and to otherwise economically rebuild an engine requiring balance shaft and drive component replacement.
It is another object of the present invention to provide a retrofit kit of the aforesaid nature which will increase the engine's horsepower and operating oil pressure.
It is still another object of the present invention to provide a retrofit kit of the aforesaid nature which is simple to install, durable in construction, resistant to failure, and amenable to low cost manufacture.
These and other beneficial objects and advantages will be apparent from the following description.